The present invention relates to a control apparatus and a control method, more particularly to a control apparatus and a control method that are suitable for application to a disk array apparatus designed to control the rotation of cooling fans based on the logical sum of control signals output from dual controllers.
In recent years, a single disk array apparatus is equipped with a plurality of cooling fans for cooling the inside of the chassis. By driving the cooling fans with low or high speed rotation, depending on the situation, heat generated from hard disk drives and various circuit boards and other components installed inside the chassis is efficiently discharged outside.
The rotation control of the cooling fans in the above-described case is conducted by using wired-OR connection to the respective output lines of the dual controllers in order to reduce the number of cables, and thereby gives a logical sum of rotation instruction signals, as control signals output from each controller (for example, a high-level signal for high-speed rotation, and a low-level signal for low-speed rotation) to the cooling fans through a single signal line.
The rotation state (rotation rate) of the cooling fans is detected by a rotation sensor installed for the fans and fed back to each of the controllers. Accordingly, each controller can detect, based on a sensor output of the rotation sensor, a rotation malfunction of the cooling fans, such as outage or low-speed rotation of the cooling fans in spite of a high-speed-rotation order from the controller.
JP Patent Laid-Open Publication No. Hei 8-195760 discloses a defect detecting system including a plurality of slave devices that are connected to each other in a multi-dropped wired-OR connection. Each slave device is equipped with: a transmission circuit for processing transmission data in a baseband into time-divided transmission data and outputting this data; a monitoring circuit for monitoring the time-divided transmission data and outputting an output blocking control signal when detecting a malfunction; and an output blocking circuit for physically blocking transmission of the time-divided transmission data input from the transmission circuit when the output blocking control signal is supplied from the monitoring circuit. Accordingly, this system can identify a defect in any of the slave devices connected to each other in the multi-dropped wired-OR connection, while minimizing any effect that the defective slave device may have on the other slave devices.